Judiceratops tigris

Judiceratops tigris is a horned dinosaur from the Campanian of the Judith River Formation in Montana. It's a reasonably common animal there- four specimens are known- but unfortunately all of them are highly incomplete. Never the less, there is enough of the parietal- the diagnostic bit of the animal- to show that it's a new species. The back of the frill is broadly arched and has very low hornlets; the hornlets on the side of the frill become much larger towards the front, with large, ear-shaped hornlets at the front of the squamosals.

Parietals and the associated hornlets turn out to be hugely diagnostic. This seems odd: the hornlets are formed in association with large scales, so we are in effect seeing what the dinosaurs' scales look like. But in fact, scales turn out to be highly diagnostic for living species such as snakes and lizards.

The beauty of scales is that they don't change much over the course of the animals' lifetime: a baby hatches out with a particular scale pattern and it doesn't change much. That's the same reason we use fingerprints to ID people. Unlike bone- which is hard, but which changes a lot as an animal matures- skin is flexible, but the patterns in it- scale patterns, fingerprint whorls- are incredibly stable over time.

Judiceratops is one of the oldest known chasmosaurs, although that's hardly surprising given that centrosaurs- the chasmosaurine sister group- are known from the same time period. It already shows a lot of the diagnostic features of the Chasmosaurinae - and the centrosaurines of the day also showed characteristic features of Centrosaurinae- suggesting we are missing a lot of ceratopsian evolution. The early Campanian and Santonian probably had a lot going on in terms of ceratopsid evolution, but we don't know anything about it because we don't have rocks from that age.

Judiceratops is named, obviously enough, after the Judith River. It's called tigris because its' from the Princeton collection (their mascot is the tiger). This was partly to honor Princeton's contributions to vertebrate paleontology- and partly to tweak the nose of the Yalies by naming a dinosaur after another school.

Paper here: http://www.bioone.org/doi/abs/10.3374/014.054.0103